ZURICH (Reuters) - Activist hedge fund investor Elliott Management Corp. has trimmed its stake in Swiss duty-free retailer Dufry AG in December to less than 1 percent, the SIX Swiss Stock Exchange reported over the weekend. The stock had risen more than 10 percent from when Reuters reported Elliott’s 5.6 percent holding on Dec. 20 until late January, before shedding much of that gain in recent trading...